Injection molding machine



Jan. 10, 1950 R. w. DINZL INJECTION MOLDING MACHINE 5 Sheets-Sheet 1Filed Jan. 28, 1947 l llllll ll|!ll INVENTOR fi /Cf/APD W 001 24 BY W 'WY ATTORNEYS Jan. 10, 1950 R. w. DINZL INJECTION MOLDING MACHINE FiledJan. 28) 1947 5 SheetsSheet 2 INVENTQR W 0/4 24 RNEES R. W. DINZLINJECTION MOLDING MACHINE Jan. 10, 1950 Filed Jan 28, 1947" 5Sheets-Sheet 3 N LI INVENTOR HOV/4P0 W fi/n ZL BY W p ATTORNEYS Jan. 10,v15 50 w. z 2,493,805

INJECTION MOLDING MACHINE INVENTOR A /CHA/PQ W D/A ZL ATTORNEYS Jun.19,1950 R. wbmzl... 2,493,305

INJECTION MOLDING lvmcmm:

Fil'ed Jab. 2a, 1947 5. Sheets-Sheet 5 INVENTOR HOV/4P0 ll/ D/A/ZLATTORNEYS Patented Jan. 10, 1950 UNITED STATES PATENT OFFICE INJECTIONMOLDING MACHINE Application January 28, 1947, Serial No. 724,891

11 Claims.

This invention relates to injection molding machines.

In the conventional type injection molding machine, a charge of granularmolding material is forced through a heated injection cylinder underhigh pressure by a plunger to plasticize the molding material anddeliver it to a mold in which the material is maintained under highpressure over a period of time, after which the plunger is retracted andthe material in the mold is allowed to cool for a further period of timewhile the plunger remains at rest and an additional charge of granularmolding material is fed to the injection cylinder. The plunger isoperated hydraulically and pumping equipment is employed to develop thehydraulic pressure required for operation thereof. The pumping equipmentis actually made use of only during the injection and retraction strokeof the plunger but operates continuously. In large capacity machines,large pumping equipment and expensive heating equipment for theinjection cylinder are required, thus adding materially to the initialcost as well as the operating cost of such machines. As between twomachines of different capacities, the ratio of the initial cost andoperating cost of the large capacity machine to the small capacitymachine, materially exceeds the ratio of the capacities. It istherefore, of importance to a manufacturer of injection molding machinesto minimize as much as possible the heating and power requirements oflarge capacity machines.

An object of this invention is an injection molding machine of suchstructure as to minimize its initial cost and power requirements and tomake maximum utilization of its power equipment.

In a machine embodying the present invention, a charge ofpre-plasticized molding material in small increments is supplied to theinjection cylinder during the cooling period and the plasticizedmaterial is introduced into the injection cylinder in such manner as toeffect retraction of the injection plunger. The pre-plasticized moldingmaterial increments are supplied to the injection cylinder from a smallauxiliary heating cylinder into which granular molding material isintroduced and forced through said cylinder by hydraulic pressuredeveloped by the pump equipment during the period which in injectionmolding machines heretofore used the pumping equipment was idling. Durinits passage through the auxiliary cylinder, the molding material ispartially or completely plasticized. The pressure required for operatingthe injection plunger is less than would be the case if a charge ofgranular molding material were introduced into the injection cylinderand such equipment is utilized during throughout substantially theentire injection cyle. The heating unit required for pre-plasticizingthe molding material is correspondingly smaller and the heating unit forthe injection cylinder need be only sufiicient for maintaining theplasticized molding material at the proper temperature rather thansupplying sufficient heat to render the material plastic. Since, withthe molding material pre-plasticized, a lower injection pressure isrequired to advance the preplasticized molding material than wouldotherwise be the case, the injection cylinder may be of less strengthand of correspondingly lower cost and the pumping equipment necessary todevelop the plunger-operating pressure may be smaller.

Other objects, novel features and advantages of this'invention willbecome apparent from the following specification and accompanyingdrawings, wherein:

Fig. l is an elevation of an injection molding machine involving theinvention;

Fig. 2 is a plan view of Fig. 1;

Fig. 3 is a section on the line 3-3 of Fig. 1;

Fig. 4 is a section on the line 4-4 of Fig. 3;

Fig. 5 is a hydraulic diagram, and

Fig. 6 is a wiring diagram.

A frame 5 is formed with two stationary heads 6 and 1 between whichextend guide rods 8. The head 6 supports an injection cylinder 9 havingat one end a discharge nozzle I 0. A platen I! is slidably mounted onthe rods 8 for movement toward and away from the nozzle In and a secondplaten I2 is slidably mounted on the rods 8 for movement toward and awayfrom the platen I I. The platens II and I2 support die halves i3 and Mof which the latter has a passageway adapted to register with the nozzleIII in one position of the platen II. In the wall of the cylinder 9,there is provided a lateral filling port I5 and a plunger [6 is mountedin said cylinder for reciprocation toward and away from said nozzle III.The port I5 is located between the nozzle III and the nearest point ofapproach of the plunger 56 to the nozzle. Suitable means 9a are providedfor heating the cylinder 9.

The frame 5 is provided with a third stationary head I! which supports afilling cylinder I8 of materially less capacity than the cylinder 9 andhaving an outlet port l9 at one end and a lateral inlet port 29 in itscurved wall. A hopper 2| is located above the cylinder I8 and has achute 22 leading to the port 20. A torpedo 3 23, preferably of thedesign disclosed in applicants co-pending application, Serial No.624,448, filed October 25, 1945, now Patent No. 2,462,308, is arrangedin the filling cylinder l8 between its inlet port 20 and its outlet portl9. A plunger 24 is mounted in the cylinder l8 for reciprocation towardand away from the torpedo and its path of movement is such that itcovers the inlet port 20 on its forward stroke and uncovers said port onits rearward stroke. The outlet of the cylinder 9 is connected to theinlet l of the cylinder If! by a nipple 25 connected between saidcylinders in such manner as to permit slight relative movement of thetwo cylinders without breaking the connection between them. Suitablemeans 18a are provided for heating the cylinder I8.

A hydraulic motor 26 is supported by the head 6 and its piston 21 isconnected to the plunger It to effect reciprocation thereof uponreciprocation of'the piston -21 and the arrangement is such that theplunger It at no time closes the port l5. The cylinder of the hydraulicmotor 26 is provided with two ports 2'8 and 29, by means of whichhydraulic fluid is supplied to and withdrawn from opposite ends of thecylinder to eiiect reciprocation of the piston 21.

The head l1supports a hydraulic motor 30,

the piston 3| of which is connected to the plunger produces low pressureat the port 58 which is in communication with the discharge port of thevalve 45.

The valve 45 is equipped with a solenoid 5| which, when ole-energized,sets the valve 45 in such condition that both the ports 23 and 29 of thehydraulic motor 23 are connected to the port 50 of the pump 43 and whenenergized sets the valve 45 in such position that the port 29 of thehydraulic motor 26 is connected to the pump port 49 and the port 2B ofthe hydraulic motor 26 is connected to the pump port 53. The valve 41 isequipped with two solenoids 52 and 53 and the arrangement is such thatwhen both solenoids are de-energized, the valve 31 is set in suchposition that its inlet port communicates with its discharge port andboth ports 41a and 412) are blocked; that when the solenoid 52 isenergized, with the solenoid 53 de-energiZed,-the valve 41 is set insuch position that the port 19 of the pump 43 communicates withthe'ports 3i and 4] respectively of the hydraulic motors 34 and 39 withthe remaining ports of said hydraulic motors communicating with thedischarge port of the valve 41; and that, when the solenoid 53 isenergized with the solenoid 5'2 de-energized, the valve '41 is set insuch position that the .port

. 49 of the pump '43 is in communication with the ing a piston 35-connected by a rod '36 to the platen H. The cylinder of the hydraulicmotor 34 is provided with ports 31 and 38 through which hydraulic flu'idis supplied to and "withdrawn from said cylinder to effect reciprocationof the piston 35. I

The head 1 supports a hydraulic motor 39 having a piston 49 connected tothe platen 1-2 to effect reciprocation thereof upon reciprocation of thepiston. The cylinder of the hydraulic motor 39 is provided with ports"41 and '42 through which hydraulic fluid is supplied to and withdrawnfrom said cylinder to efiect reciprocation of the piston 40. I p A pump43 draws hydraulic fluid from a tank and discharges it under pressurefor operating the hydraulic motors 28, 3'5, '34 and '39. The pump has amain outlet 49 in com-munic with the supply port of each of threefour-way valves 45, 46, and E1, of which the valve '45 controls flow ofhydraulic fluid to and from the hydraulic motor '23 and the valve 46controls the flow of hydraulic fluid to and from the hydraulic motor 38while the valve 11 controls the flow of hydraulic fluid to and from boththe hydraulic motor 34 and the hydraulic motor 39. The valve has ports36a and 26b communicating -r'espectively with the ports 32 and 33o-f'th'e hydraulic motor 30, while the valve 41 has a port 31acommunicating with the ports 31 and M of the hydraulic motors 34 and 33,respectively, and a port 411) communicating with the ports 38 and d2 ofthe hydraulic motors 34 and 39 respectively. The pump 43 is a standardcommercially available pump which is so constructed that it issuperchargedby a small auxiliary pump (not shown) but integral with themain pump and the arrangement of the auxiliary pump is such that itports 38 and 42 of the hydraulic motors 3t and 39 respectively with theremaining ports of said hydraulic motors communicating with thedischarge port of the valveei. The valve it is equipped with twosolenoids 5t and 55 and the arrangement is such that when both solenoidsare de-energized, the valve 43 is set in such position that its inletport communicates with its discharge port and both ports tta and 551)are blocked; that when the solenoid '54 is energized with the solenoid55 de-en'ergized, the valve 86 is set in such position as to connect thepump port it to the port 33 of the hydraulic motor 33 with the port 34connected to the discharge port of the valve 36; and that, when thesolenoid 53 is energized with the solenoid 55 tie-energized, the valve'45 is set in such position that the pump port 49 is connected to theport 32 of the hydraulic motor'tfl with the port '33 connected to thedischarge port of "the valve 'M.

A second pump 55 draws hydraulic fluid from the tank and supplies it tothe inlet of the valve 41 at 'a higher pressure than hydraulic fluid issupplied to the valve #1 by the pump 33. A check valve 51 prevents flowof hydraulic fluid from the pump 55 to either the valve as or the valve4'6.

A self-closing limit switch 53 is provided for actuation :by the plunger1'8, the arrangement being such that the limit switch is opened by theplunger at the limit of its retraction stroke. A self-opening limitswitch 59 and a self-closing limit switch 38 are provided for actuationby the piston 3| of the hydraulic motor 36, the arrangement being suchthat the switch 59 is closed by the piston 31 at the end of its forwardstroke and the switch 60 is opened by the piston 31 at the end of itsretraction stroke. A self-closing limit switch 6| is provided foroperation by the platen l2, the arrangement being such that the switchis opened by the platen 12 at the end of its retraction stroke. Bysuitable energization of the various solenoids, the platens H and it areactuated to engage the platen ii with the nozzle I0 and to clamp the diehalves i3 and M in meldforming relation. The plunger 16 is advanced toinject molding material from the cylinder 9 through the nozzle l intothe mold formed by the die halves without closing the lateral port I andduring advance of the plunger I6, the plunger 24 is locked againstmovement. The plunger 24 is reciprocated after completion of theinjection stroke of the plunger I6 with the die halves I3 and I4 clampedto introduce several small charges of plasticized molding material fromthe cylinder I8 into the cylinder 9 to recharge the cylinder 9 andreturn the plunger I6 to original position. Upon return of the plungerI6 to its original position, the plunger 24 is locked in whateverposition it is when the plunger I6 reaches its original position. Thus,the plunger 24 prevents escape of plasticized molding material throughthe port I5 from the cylinder 9 during the injection stroke of theplunger I6. Upon each retraction stroke of the plunger 24, it uncoversthe port 26 to admit a charge of granular solid molding material intothe cylinder I8 and upon each advance stroke of the plunger 24, thenewly admitted charge is advanced toward the torpedo 23 and a smallamount of plasticized molding material is discharged through the nippicinto the injection cylinder 9. The return of the plunger I6 to itsoriginal position takes place during the curing period of the piecebeing molded and such period is longer than is necessary to introducethe required number of charges of plasticized molding material from thecylinder I8 into the cylinder 9 to recharge the latter. Upon completionof the curing period, the platens II and I2 are returned to theiroriginal positions to open the die halves and disengage the platen II,from the nozzle. After removal of the molded piece, the machine is readyfor another operation. The pump 56 supplies clamping pressure for thedie halves, during the molding and curing periods.

Energization of the solenoids is effected by the electrical system ofFig. 6 in which L is one conductor and L is the other conductor of acurrent supply. The conductor L is connected to the conductor L' througha starting switch 62 in series with a timer 63 and a shunt circuitaround the switch 62 contains the limit switch 6| and the contact 630.of the timer 63. The conductor L is also connected to the conductor L asfollows: through the timer contact 63b and relay 65, through thenormally open contacts 65a of the relay 65 and the solenoid 53, throughthe normally closed contacts 65b of the relay 65, limit switch SI andsolenoid 52, through the normally open contacts 630 of the timer 63 andthe solenoid 5I, through the timer contacts 63d, limit switch 58, thelimit switch 59 and the relay 66. A shunt circuit around the switch 59contains the limit switch 66 and the normally open contacts 66a of therelay 66. A shunt circuit around the switch 59 and the relay 66 includesthe normally closed contacts 662) of the relay 66 and the solenoid 54,while still another shunt circuit around the switch 59 and the relay 66includes the normally open contacts 660. of the relay 66 and thesolenoid 55.

Assuming that the cylinder 9 contains a full charge of plasticizedmolding material with the plunger 24 in any position in the cylinder I8and that the platens II and I2 are in their retracted positions, theoperation of the device is as follows: The operator pushes the startbutton 62 which energizes the timer 63, the initial operation of whichcloses the contact 63a, but does not close the shunt around the starterbutton 62 as the limit switch 6I is held open by the platen I2.

Further advancement of the timer 63 closes the contacts 631) to energizethe relay 65. Energization of the relay 65 closes the contacts 65a toenergize the solenoid 53 and opens the contacts 651) to preventenergization of the solenoid 52, whereupon the valve 41 is set todeliver hydraulic fluid to the port M of the hydraulic motor 30 andpermit discharge of hydraulic fluid from the port 38. Thereupon, theplaten II advances toward the nozzle II] and the platen I2 advancestoward the platen II to close the dies I3 and I4. Advancement of theplaten I2 releases the switch 6| to closed condition, therebyestablishing a holding circuit for the timer through it and the timercontact 63a after which the starting switch 62 may be released. Furtheradvancement of the platen I2 clamps the die I4 against the die I3 and asthe clamping takes place, the pump 56, by virtue of its higher pressuretakes over delivery of hydraulic fluid to the port ll and operatesagainst the check valve 51 to seal off the clamping circuit from theremainder of the machine.

Continued advancement of the timer closes the timer contacts 630 toenergize the solenoid 5i. Energization of the solenoid 5| sets the valve45 to deliver hydraulic fluid from the pump 43 to the port 29 of thehydraulic motor 26 and permit the discharge of hydraulic fluid from themotor through the port 28, thereby causing advancement of the plunger I6to discharge the plasticized molding material from the cylinder 9 intothe mold. Advancement of the plunger I6 releases the limit switch 58 toclosed position. By reason of both solenoids 54 and 55 being(la-energized, the ports 46a and 46b of the valve 46 are blocked,thereby locking the piston 3! so that in the event the plunger 24 is inany position other than at the end of its retraction stroke, it is heldin such position irrespective of the pressure applied to it by moldingmaterial in the cylinder 9. After completion of the injection stroke ofthe plunger I6, the timer contacts 630 open to de-energize solenoid 5i,whereupon the valve 45 automatically is set in position to block off itsinlet port and connect the ports 28 and 26 of the hydraulic motor 26 tothe port 56 of the pump 43, thereby applying to both faces of the piston27 the pressure existing at the port 56. Because of the different areaof the two faces of the piston 21, the latter, as well as the plunger I6is held at the end of its forward stroke until some greater force movesit back. Further advancement of the timer 63 closes the normally opencontacts 63d, thereby closing a circuit through the limit switch 58,normally closed contacts 6% of the relay 66, and the solenoid 54.Energization of the solenoid 54 sets the valve 46 in positionto supplyhydraulic fluid to the port 33 of the hydraulic motor 36 and permitdischarge of hydraulic fluid from the port 32, thereby advancing theplunger 24 to supply plasticized molding material from the cylinder I8to the cylinder 6. Since the dies are closed and a piece has just beenmolded, the discharge nozzle IE1 is plugged by molding material. Themolding material being delivered to the piston 6 cannot escape throughthe nozzle and, therefore, forces the plunger I6 back against the lowpressure existing on the rear face of the piston 27. The amount ofplasticized molding material thus delivered is less than the capacity ofthe cylinder 9. When the piston 3| completes its forward stroke, itoperates limit switch 59 to closed position, thereby energizing relayG6, energization of which closesits normally open contacts 66a, therebylocking the relay in actuated position through the switch 80'. Actuationof the relay 66 also opens its normally closed contacts 66b and closesits normally open contacts 660, thereby energizing the solenoid e.Energization of the solenoid shifts the valve 46 into condition todeliver hydraulic fluid from the pump 43 to the port 32 of the-hydraulicmotor 30 and permit discharge of hydraulic fluid through the port 33,thereby eiiecti-hg retraction of the piston 31 and the plunger 34. Fullretraction of the plunger 24 uncovers the port 26, permitting a newcharge of molding material to fall in ahead of the plunger 24. Also,full retraction of the piston 3 foperates the switch to open position,thereby tie-energizing relay 66. De-energization of the relay 66 closesthe contact 66b to close the energizing circuit of solenoid 54' andopens the contacts (56c to d e-energize the solenoid 55. The piston 3iagain moves forward to deliver! a. charge of plasticized material intothe cylinder 9. Reciprocation of the piston 35 continues until theplunger I6 is moved to a position in which it opens the switch 58.Opening of the switch 58 ale-energizes both solenoids 54 and 55,whereupon the valve 46 assumes the position in which both the ports 32and 33 of the hydraulic motor Ell are blocked, thus locking the plunger24- 1 against movement. The timer contact 63b now opens to de-energizethe relay Die-energization of the relay 65- opens the contacts 65a andcloses the contacts 65b, thereby de-energizing the solenoid 53 andenergizing the solenoid 2;.

52 through the switch. ti. Energization of the solenoid 52 sets thevalve 41 to deliver hydraulic fluid to the ports 38 and 42 of thehydraulic motors 34 and 39 respectively, while permitting escape ofhydraulic fluid through the ports 3? and 4|, thereby retracting theplatens .ll and i2. to open the dies. When the platen 12 com-- pletesits retraction, it operates the switch 6! to? open. position, therebydie-energizing the solenoid. 52 and the timer 63, permitting the latterto reset in anticipation of the next cycle. Since both solenoids 52' and53 are de-energized, the valve 41 is: set in neutral in which condition,the delivery of the pumps is by-passed from the inlet port to thedischarge port and thence to the tank. The machine is now ready for thenext cycle.

The pistons 35 are provided with extensions projecting beyond the head 6and the exposed end of each piston is equipped with an enlarged butten61'. ilhe head 5 supports a locking ring 63 (Fig; 1) movable into andout of position to fill in the space between the buttons El and head 5tolock the platen l I. in engagement with the nozzle ii). With thelocking ring 58 in operative position, the platen H is held stationaryduring the operation of the machine, but with the looking ring. 68 ininoperative position, the platen ii is reciprocated relative to thenozzle it? during operation. of the machine.

It is of course. understood that various modifications may be made inthe injection molding machine above described, without in any waydeparting from the spirit of the invention as defined in the appendedclaims.

A pre-plasticizing injection molding machine incorporating theprinciples disclosed hereinabove, inherently transfers thepro-plasticized molding material, through the nipple connection 25 andinto the injection cylinder 9, with the material under compressionduring its transfer-'- ring flow movement and continuously while in theinjection cylinder. In efiect, the pro-plasticizin-g plunger 24'incrementally efiects injection molding of the plasticized material intothe injection cylinder 9, with the injection molding pressuresubstantially equaling the force applied the injection plungerv l6 bythe piston 2'! when the pump pressure is applied. to both the ports 23and 29. The flow-resistance provided by the connection 25 prevents thematerial backing therethrough from the injection cylinder, thus. keepingthe material under compression in this cylinder during reciprocation ofthe pre-plasti-- sizing plunger.

Prior art injection molding machines, of this general type, incorporatean injection plunger 'reciprocator which can be controlled only toadvance and return this plunger. The plungeradvancing force provides thefull injection mold-r ing force, and no arrangement is provided forreducing this force. Therefore, the injection plunger must be fullywithdrawn during charging of the injection cylinder, thepre-plasticising assembly or system- 'therefor discharging into emptyspace. This space is in the injection moldcyli-nder andthe latter isheated, as contrasted to the empty space in the die cavity where thedesired injection molding is produced, the dies being" customarily cold.Therefore, voids or gas bubbles form in the charge of the injectioncylinder. This trouble has seriously interfered with the use of thistype of machine.

Application of the principles of the present invention to apre-plasticizinginjection molding machine, inherently avoids theformation of voids or gas bubbles forming in the pre-plasticizedmaterial charged into the injection cylinder. Since such a machine,constructed in accordance with I the present invention, keeps thepre-plasticized material under compression while it is moving into theinjection cylinder, and since the latter is always kept completelyfilled with the material under compression, the described trouble ispre-' vented.

The principles of the invention provide the added advantage that thevolume of the injec ticn molding, charge, is measured in itspreplasti'cized condition directly in the injection molding cylinder.The usual practice has been tocharge measured volumes in thepro-plasticizing cylinder, this requiring compensation for the volumereduction resulting when granular thermo-plastic' material isplasticized by the heat and pressure.

i. In a molding machine, an injection cylinder having a nozzle at oneend, a plunger reciprocable in said injection cylinder, a lateral portin said cylinder between said nozzle and the nearest point of approachthereto of injection'plunger, a filling cylinder of less capacity thansaid injection cylinder communicating with said injection cylinderlateral port and having a lateral port, a plunger reciprocable in saidfilling cylinder across the lateral port thereof, a molding materialsupply chute communicating with said filling cylinder l-at'eral port, asource of hydraulic fluid under pressure, means for utilizing saidhydraulic fluid to force said injection plunger toward the injectioncylinder nozzle, means biasing: the injection plunger against return.movement after completion of the injection stroke, means efiective uponcompletion. of the injection stroke of the injection plunger toutilizesaid hydraulic fluid to effect reciprocation of the filling plungerthereby introducing plasticized molding material into said injectioncylinder and causing return of the injection plunger under pressureexerted by the introduced molding material, and means effective uponcompletion of the return of the injection plunger to discontinuereciprocation of said filling plunger and lock the same againstmovement.

2. In a moldingmachine, an injection cylinder having a nozzle at oneend, a plunger reciprocable in said injection cylinder, a lateral portin said cylinder between said nozzle and the nearest point of approachthereto of said injection plunger, a filling cylinder of less capacitythan said injection cylinder communicating with said injection cylinderlateral port and having a lateral port, a plunger reciprocable in saidfilling cylinder across the lateral port thereof, a molding materialsupply chute communicating with said filling cylinder lateral port, afirst hydraulic motor operatively connected to said injection plunger, asecond hydraulic motor operatively connected to' said filling plunger, ahigh pressure source of hydraulic fiuid, a" low pressure source ofhydraulic fluid, means including a first valve for supplying highpressure or low hydrau lic fiuid to said first hydraulic motor, meansincluding a second valve for supplying high pressure hydraulic fiuid tosaid second hydraulic motor, means controlled by said injection plungerfor operating said first valve to connectsaid high pressure source tosaid first hydraulic motor to advance said injection cylinder plunger,means for operating said first valve to connect said low pressurehydraulic source to said first hydraulic motor after completion of theadvance stroke of the injection plunger to oppose the return strokethereof, means effective upon completion of the advance stroke of theinjection plunger to operate said second valve to supply hydraulic fluidto said second hydraulic motor to effect reciprocation of the fillingplunger to introduce plasticized molding material from said fillingcylinder into said injection cylinder and thereby cause return of theinjection plunger, and means effective upon completion of the returnstroke of the injection plunger to operate'said second valve todiscontinue operation of said filling plunger and lock it againstmovement.

3. In a molding machine, an injection cylinder having a nozzle at oneend, a plunger reciprocable in said injection cylinder, a lateral portin said cylinder between said nozzle and the nearest point of approachthereto of said injection plunger, a filling cylinder of less capacitythan said injection cylinder communicating with said injection cylinderlateral port and having a lateral port, a plunger reciprocable in saidfilling cylinder across the lateral port thereof, a molding materialsupply chute communicating with said filling cylinder lateral port, ahigh pressure source of hydraulic fluid, a low pressure source ofhydraulic fluid, a first two-port hydraulic motor operatively connectedto said injection plunger, means adapted either to connect one port tothe high pressure source or both ports to the low pressure source andincluding a first Valve, a second two-port hydraulic motor operativelyconnected to the filling plunger, means including a second valve adaptedselectively to connect said second motor ports alternately to said highpressure source to effect reciprocation of said filing plunger or toblock both said ports to hold said filling plunger stationary, andcontrol means efiective first to set said second-valve in position tohold said filling plungerstationar-y and said first valve in position toconnect said high pressure source to said one port of the firsthydraulic motor to advance said injection plunger and second to set saidfirst valve in position to connect said low pressure source to bothports of said first hydraulic motor to oppose return of said injectionplunger and third to set said second valve in position to effectreciprocation of said filling plunger to introduce plasticized moldingmaterial from said filling cylinder into said injection cylinder until.full return of said injection plunger under pressure exerted by theintroduced molding material and fourth to reset said second valve inposition to hold said filling plunger stationary.

4. In a molding machine, an injection cylinder having a nozzle at oneend, a plunger reciprocable in said injection cylinder, a lateral portin said cylinder between said nozzle and the nearest point of approachthereto of said injection plunger, a filling cylinder of lesscapacitythan said injection cylinder communicating with said injectioncylinder lateral port and having a lateral port, a plunger reciprocablein said filling cylinder across the lateral port thereof, a moldingmaterial supply chute communicating with said filling cylinder lateralport, a high pressure source of hydraulic. fluid, a low pressure sourceof hydraulic fluid, means including a first valve connecting said firstmotor to said high pressure and lowpressure sources, control means forset ting said first valve successively to supply high pressure fluid tosaid motor to advance the injection plungerand low pressure fiuicl tosaid motor 'to oppose return of said injection plunger, means includinga second valve connecting said-second hydraulic motor' to said highpressure source, and control means including'said injection plunger forsetting said second valve to supply high pressure fluid to said'secondhydraulic motor to reciprocate said filling plunger after advancement ofsaid injection plunger to charge said injection cylinder withplasticized molding material and subsequently return said injection.plunger to original position and setting said second valve to preventescape of hydraulic fluid from said second hydraulic motor to hold saidfilling plunger stationary during the advance stroke of said injectionplunger, and means for rendering said control means operative.

5. In a molding machine, an injection cylinder having a nozzle atoneend, a plunger reciprocable in said injection cylinder, a lateral portsaid cylinder between said nozzle and the nearest point of approach,thereto of said injection plunger, a filling cylinder of less capacitythan said injection cylinder communicating with said injection cylinderlateral port and having a lateral port, a plunger reciprocable in saidfilling cylinder across the lateral port thereof, a molding materialsupply chute communicating with said filling cylinder lateral port, afirst hydraulic motor operatively connected to said injection plunger, asecond hydraulic motor operatively connected to said filling plunger, ahigh pressure source of hydraulic fluid, a low pressure source ofhydraulic fluid, a first four-way valve having two ports connectedrespectively to said high pressure hydraulic source and said lowpressure hydraulic source and two ports connected to said firsthydraulic motor, a second four-way valve having two ports connected tosaid second hydraulic motor and a third port connected to said highpressure source, and control means for setting said valves to supplyhigh pressure hydraulic fluid to said first hydraulic motor to advancesaid injection plunger and to said second hydraulic motor to hold saidfilling plunger stationary and subsequently setting said valves tosupply low pressure hydraulic fluid to said first hydraulic motor to.oppose said injection plunger return stroke and high pressure hydraulicfluid to said second hydraulic motor to' effect reciprocation of saidfilling plunger to introduce plasticized molding material from saidfilling material into said injection cylinder and returnsaid injectionplunger to its original position under pressure exerted by theintroduced molding material, and finally setting said second valve todiscontinue reciprocation of and hold stationary said filling plungerupon arrival of said injection plunger at its original position.

,6. a molding machine, an injection cylinder having a nozzle atone end,a plunger reciprocable in said injection cylinder, a lateral port insaid cylinder between said nozzle and the nearest point of .approachthereto of said injection plunger, a filling cylinder of less capacitythan said injection cylinder communicating with said injection cylinderlateral port, .a plunger reciprocable in said filling cylinder acrossthe lateral port thereof, means to .advance .said injection plunger,means to oppose the returnstroke of said injection plunger, means tomaintain said filling plunger stationary during the advance stroke ofsaid injection plunger and to effect reciprocation of said fillingplunger after themjection plunger completes its advance stroke, andmeans :to' discontinue reciprocation .of and "hold stationary saidfilling plunger upon return of said injection plunger to its originalposition. a

An injection molding machine subecombina,

tion comprising aninjection cylinder and plunger, a system for ejectingflowing substantially preeplasticized molding material, a connectionlconduc-ting said material from said system; into 'for applying variableadvancing force tosaid plunger, and controls for said system and saidactuator and causing operation of said system while reducing said forceof said actuator at least enough to permit said flowing material toreturn said plunger .by' acting on its said working end while chargingsaid cylinder with said material.

v 8. The sub-combination defined by claim 7 but further comprising acontroller actuated by a predeterminable return displacement of saidplung- 12 or .and stopping operational said system when so actuated andthus controlling the amount of said material charged-by said system intosaid cylinder.

9. 'The sub-combination defined by claim "7 but with said controlsreducing said force of said actuator to a predetermined positiveadvancing force .sufiicient to keep said material under compressionwhile in said cylinder but insufficient to prevent said return of saidplunger.

iii. A preplasticizing injection molding machine including thecombination of a die clamp, an actuator for operating said clamp to openand close the injection molding die parts, an injection (cylinder andplunger with the former constructed to inject "plasticized moldingmaterial into said die parts when they .are closed and said plunger isadvanced, an {actuator for applying variable advancing force to saidinjection plunger, a :pre-plasticizing cylinder and plunger with theformer upon advance of the latter ejecting a flow of pre-plasticizedmolding material into said injection cylinder to the working end of saidinjection'plunger when the latter is at an advanced position, areciprocator for said preeplasticizing plunger, and a control system forsaid injection plunger actuator, said control system reducing theadvancing torce it applies to said injection plunger, while permittingoperation of said die clamp actuator and of said pre-plasticizingplunger reciprocator in a plunger advancing .manner, to a force lessthan the force exerted in feombination further including a controlsystem a return direction by said pre-plasticized material actingagainst said injection plungers working zend, whereby to in effect causeinjection 'molding of saldpre-plasticized moldingmaterial into' saidinjection cylinder under a pressure related to said reduced advancingforce applied said injection plunger.

11. The machine defined by claim 10 with said for said pre pla'sticizingplunger re'ciprocator and which includes a controller, actuated by apredeitermined return displacement of said injection "plunger, forstopping operation of said reciprocator, whereby to control the amountof said preplesticized material injection-molded into said injectioncylinder.

' RICHARD W. DINZL.

'file of this patent:

UNITED STATES PATENTS Number Name Date 2,107,190 Shaw Feb. 1, 19382,465,889

Lester et a1 Mar. 29, 1949

